Ways to increase endurance of the refractory lining in converters

Abstract

Based on the expertise gained in the use of a 350-ton converter at the WSIWS Joint-Stock Co., blowing facilities and regimes have been modified. Low-temperature slag splashing is numerically simulated for a top-blown tuyere using tips with single and double-row nozzle arrangement. A slag-splashing tuyere fitted with a steel tip with a double-row arrangement of nozzles has been designed. Ways to improve the melting technology using modified tuyeres combining slag splashing and flame gunning operations and to improve repair of the lining using a vertical tuyere are proposed.At the WSISW Joint-Stock Co., the vessel campaign in converter-based steelmaking technology (with slag containing 8 -14% MgO) could be extended to 2500 -3000 heats (using techniques such as slag splashing, extra gunning, and repair of the refractory lining); for comparison, the vessel campaigns reported from the Magnitogorsk Iron and Steel Works (MISW) were 3700 -4000 heats [2], and from the Severstal' JSC, 4500 heats [3]. Foreign manufacturers, owing to the effective use of auxiliary techniques and equipment (mechanical drive, cooling systems for the converter and tuyeres, systems for escape, treatment, and entrapment of the converter gas, transfer facilities for steel and slag), could extend the vessel campaign to 30,000 heats or even more [4 -7]. Furthermore, a common practice with foreign manufacturers is the prerefining of iron prior to the converter process, careful scrap preparation, and the use of advanced automation [8,9]. The use of dynamic systems for controlling the melting process makes it possible to maintain a high efficiency (reaching 90%) in the control of carbon content ± 0.02% and melting temperature ± 12°C even in the early stage of charging a converter. Laser-based measuring systems [10] provide information about thickness of the refractory lining throughout the course of a campaign, which makes it possible to enhance the efficiency of repair of the lining, for example, by slag blowout or gunning.Melting techniques as commonly practiced in the domestic converter technology prescribe the removal of sulfur and phosphorus (as high as possible) prior to the blow of the bath; the hot repair of the vessel lining is commonly made by applying the lining slag, or the scull, by blowing out the final slag for this purpose, or by flame gunning using a patching material based on calcined magnesite or dolomite.Introduction of a technology for blowing out the final slag (containing 8 -14% MgO) with nitrogen injected through the top-blown oxygen tuyere turned out to be a challenging problem for foreign [6,7] and domestic technologists [11,12]. A rational idea was to use a special elongated tuyere [13]. Such tuyeres were employed to good effect to blow out slag with nitrogen at a flow rate of 320 -500 m 3 /min in 375-ton converters at the MISW JSC [12]. However, later the idea was abandoned, and for slagging the lining, technologists continued to use conventional oxygen tuyeres to blow nitrogen at a flow rate of 900 -1200 m 3 /min [2]. The o...